Lithium ion batteries have the advantages of high open-circuit voltage, high energy density, long service life, no memory effect, little pollution, small self-discharge rate and the like, and the overall performances are better than those of other traditional secondary batteries, thereby being consistently considered to be the most ideal power supplies for various portable electronic equipment and electric vehicles. Although graphite, which is a traditional lithium ion battery negative electrode material, has good cycle stability and relatively high performance-price ratio, but because the charge-discharge specific capacity is lower and the volume specific capacity has no advantage, graphite hardly meets the requirements of power systems, in particular to electric vehicles and hybrid electric vehicles for high capacity of the batteries. Therefore, it is very urgent to develop novel lithium ion battery negative materials with high specific capacity, high charge-discharge efficiency and long cycle life. In the studies of the novel non-carbon negative electrode materials, due to the highest theoretical lithium intercalation capacity (4200 mAh/g, which is much higher than that of all the other current negative electrode materials), Si-based materials have attracted more and more attention. If Si-based negative electrodes can achieve the practical degree, the range of applications of the lithium ion batteries will surely be greatly expanded. However, the Si-based materials have serious volume effect under high-degree lithium deintercalation conditions, thereby resulting in a significant decline in cycle stability of electrodes. Against the volume efficiency of silicon, silicon is compounded with a carrier with elasticity and stable performances to buffer the volume change of silicon, so that this way will be an effective one for keeping the high capacity of silicon and simultaneously improving the cycle stability thereof. Carbon has the advantages of lighter mass, better electric conductivity, lower lithium intercalation electric potential, small volume change during a lithium deintercalation process, low price and the like, thereby being widely applied in Si composite materials. In recent years, conductive polymers, such as polyaniline, polypyrrole and the like, are also tried as objects of the Si composite materials due to high electric conductivity, good lattice elasticity and the like. As organic polymer materials, the conductive polymers can also be used as carbon sources for preparing carbon materials. Wang et al. prepared carbon spheres with the diameter of less than 100 nm, which are doped with N atoms, by carbonizing polypyrrole nano-spheres; and by applying the carbon spheres to the negative electrodes of the lithium ion batteries, the batteries can still keep the reversible capacity of 400 mAh·g−1 after 60 cycles of operation (Ind. Eng. Chem. Res., 47(2008): 2294-2300). But till now, only Zhang et al. took polyparaphenylene in the conductive polymers as the carbon source for preparing a Si/C composite material for researching the negative electrodes of the lithium ion batteries (J. Power Sources, 125(2004): 206-213.).
The conductive polymer poly-ethylenedioxythiophene (PEDOT) has attracted much attention of people due to the extensive application prospects. The conductive polymer in a doping state has excellent performances including high electric conductivity, high stability in structure and electric conductivity in air and the like, thereby becoming a new research hotspot of the conductive polymers. The PEDOT in the eigenstate has very poor electric conductivity and is non-melt and insoluble, and polystyrene sulfate (PSS) radical anion-doped PEDOT can be dispersed and dissolved in a water solution, is very stable in the air after being coated to form a film and simultaneously has high electric conductivity; and furthermore, the water solution can be further processed so as to greatly promote the application of the PEDOT. So far, PEDOT or PEDOT: PSS has been mainly used as a positive electrode material of the lithium ion battery (Electrochim. Acta, 53(2008): 8319-8323), or used for related research as a composite material for a positive electrode (Electrochem. Commun., 4(2002): 545-549). The structure unit of each of PEDOT and PSS contains one S atom, and the carbonized material thereof may be doped with a small amount of heteroatom S. However, Yu et al. believed that the formation of a —C—S—C— bond in the carbon material is more conductive to insertion of lithium ions (J. Power Sources, 108(2002): 245-249). Therefore, the novel Si/C composite material doped with the small quantity of S atoms can be further prepared by preparation of a Si/PEDOT: PSS composite material followed by carbonization treatment.